Vehicles may be fitted with evaporative emission control systems to reduce the release of fuel vapors to the atmosphere. For example, vaporized hydrocarbons (HCs) from a fuel tank may be stored in a fuel vapor canister packed with an adsorbent which adsorbs and stores the vapors. At a later time, when the engine is in operation, the evaporative emission control system allows the vapors to be purged into the engine intake manifold for use as fuel. However, leaks in the emissions control system can inadvertently allow fuel vapors to escape to the atmosphere. Thus, various approaches are used to identify such leaks.
One such approach for leak detection includes sealing off the fuel tank, canister, and various conduits from atmosphere and applying pressure to the sealed off system, via a vacuum pump for example. Once a threshold pressure has been reached in the system, the pump may be shut off and leaks may be detected based on a rate of bleed-up or bleed-down of the pressure. However, the vacuum pump utilizes a separate motor, thus consuming additional energy and reducing fuel economy.
The inventors have recognized the above issues and offer a method to at least partly address them. In one embodiment, a method comprises driving a cooling fan with an electric motor in a vehicle, and during selected conditions, also driving a vacuum pump with the electric motor through a clutch.
In this way, a motor used to drive a vehicle cooling fan may also drive a vacuum pump. In one example, the vacuum pump may be operated to apply vacuum to a fuel system of the vehicle during a fuel system leak detection test. By using an existing motor of the vehicle, additional energy expenditure by the engine to drive the vacuum pump may be reduced. Further, the cooling fan may continue to be operated after an engine shut off to ensure adequate engine cooling, thus allowing the vacuum pump to be driven, and hence the leak detection test performed, while the engine is not operating. In doing so, factors that may confound accurate leak detection, such as high engine temperature, fuel sloshing, etc., may be reduced.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.